Washington ? There probably isn’t a tail-wagging gene or a face-licking gene. But there undoubtedly are groups of genes that explain why retrievers chase sticks, spaniels jump in the water at every opportunity, and border collies like to herd sheep and small children.

The biological basis of the astonishing variety of behaviors of man’s best friend is a big step closer to comprehension with the publication today of the dog’s genome – its 2.41 billion nucleotides, or DNA “letters.”

The dog – in the form of a female boxer named Tasha – joins the human being, the chimpanzee, the mouse and the rat on the list of mammals whose genetic instruction manual has been read and transcribed. The genomes of the fruit fly, a microscopic worm, yeast and several bacteria have also been decoded.

But the dog genome is far more than a curiosity. It is already providing insights into evolution and will likely make dogs the chief tool for understanding the genetic diseases of people.

Certain breeds are at much higher risk than others for specific ailments. Samoyeds have a tendency to become diabetic, Rottweilers get the bone cancer osteosarcoma, springer spaniels are at risk for epilepsy, and Doberman pinschers suffer from narcolepsy much more often than other canines. All these diseases have human counterparts.

“This offers a strategy for tracking down the location of genes involved in medical conditions that in the past we have just not been able to tackle,” said Francis Collins, director of the federal government’s National Human Genome Research Institute, which helped pay for the work.

The work is the product of nearly 250 scientists organized through the institute, in Cambridge, Mass. A much less detailed version of the dog genome by a different research group was published two years ago.